Gear finishing machine



A ril 7, 1964 T. s. GATES GEAR FINISHING MACHINE 6 Sheets-Sheet 1 Filed April 9, 1962 II v J Jt J INVENTOR.

.BY M

April 7, 1964 T. s. GATES GEAR FINISHING MACHINE e sneaks-sheet 2 Filed April 9, 1962 INVENTOR. THOMAS S. GATES ATTO R N EYS 6 Sheets-Sheet 3 T. S. GATES GEAR FINISHING MACHINE April 7,1964

Filed April 9, 1962 ATTORN YS April 7, 1964 s, GATES 3,127,813

GEAR FINISHING MACHINE Filed April 9, 1962 6 Sheets-Sheet 4 I24 I s so INVENTOR. THOMAS .GATES BY W i ATTO RN April 7, 1964 T. SJGATES 3,127,813

GEAR FINISHING MACHINE filed April 9, 1962 6 SheetsSheet 5 Fl G 7 INVENTOR.

BY GATES ATTO R NE April 7, 1964 T. s. GATES GEAR FINISHING MACHINE 6 Sheets-Sheet 6 Filed April 9, 1962 l Hummus 1 ummrnnuwmlmwmugw we vow OON INVENTOR. BY GATL-ZS gay/43% ATTO R N EY g ma QOE

United States Patent 3,127,813 GEAR FiNISHlNG MACHINE Thomas S. Gates, Grosse Pointe Woods, Mich, assignor to National Breach & Machine Company, Detroit, Mich, a corporation of Michigan Filed Apr. 9, 1%2, Ser. No. 138,294 23 Claims. (Cl. 9tl--1.6)

The present invention relates to a gear finishing machine.

The present application is a continuation-in-part of my prior copending application Serial No. 765,463, filed October 6, 1958, now abandoned.

The present machine has been developed primarily for use in honing gears in an operation in which a gearlike honing tool is maintained under relatively light pressure at least initially, with respect to a hardened work gear. Of course, the machine may also be used for other operations such for example as gear shaving.

It is an object of the present invention to provide a gear finishing machine in which a gear member and gear-like tool member are operated in mesh, including a pivoted support for one of said memberslocatedadjacent a vertical plane passing through its center of mass.

It is a further object of the present invention to provide a gear finishing machine comprising a base, a tool head, a tool support pivoted to said tool head for rocking movement having a substantial horizontal component, a work support on said base adapted to support a work gear in a position to be engaged by a tool, and means for applying a relatively small total force to the pivoted tool support to cause relatively light controlled pressure between the teeth of a gear and tool.

It is a further object of the present invention to, pro.- vide a machine as described in the foregoing in combination with means for locking the tool support in adjusted position.

It is a further object of the present invention to provide a gear finishing machine comprising a base, a tool slide including a tool, column adjustably mounted thereon, said slide being mounted on horizontal ways on the base, a tool head angularly connected to said column for adjustment about a horizontal axis, a tool support pivoted to said tool head, and a work support mounted on said base to support a work piece with with its axis horizontal in a position to mesh with a gear-like tool carried by said tool support.

It is a further object of the present invention to provide a machine as described in the preceding paragraph in which means are provided for driving the tool support in rotation including a drive motor mounted on said head, and transmission means extending between said motor and said tool support.

It is a further object of the present invention to provide a machine as described in the preceding paragraph including a crowning attachment comprising a pivot mounting for said work support, and cam means including a part carried by said tool slide.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings, illustrating preferred embodiments of the invention, wherein:

FIGURE 1 is a front elevational view of the gear finishing machine, with parts broken away.

FIGURE 2 is a side elevation of the machine shown in FIGURE 1.

FIGURE 3 is a rear elevation of the machine.

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FIGURE 4 is a plan view of the machine with the work support and stocks removed.

FIGURE 5 is a fragmentary sectional View on the line 5--5, FIGURE 4.

FIGURE 6 is a sectional view through a detail of guide structure on the machine.

FIGURE 7 is a view similar to FIGURE 2 showing a ditferent embodiment of the present invention.

FIGURE 8 is a fragmentary front elevational view of the machine shown in FIGURE 7, illustrating provision for diagonal traverse.

FIGURE 9 is a fragmentary sectional view on the line 9-9, FIGURE 8.

The machine comprises a base 11) provided with a motor 12 adapted to effect relative horizontal reciprocation between a gear and gear-like tool. Specifically, this reciprocation is provided by reciprocating the tool, and for this purpose the base 10 is provided with ways indicated generally at 14 for supporting a tool slide 16. Mounted on the tool slide 16 is a tool column 13, suitable Ways indicated at 2@ being provided for effecting adjustment of the tool column on the tool slide toward and away from a work support later to be described. This adjustment is accomplished by means of a manually rotatable feed screw 22 associated with a nut 24 fixed to the slide 16. The screw 22 is journaled in the tool column 18 and is provided with a squared end 26 for association with a suitable tool.

In the gear finishing operation it is ordinarily desirable to use a tool having a helix angle so related to that of the gear as to require the gear and tool to be brought into a crossed axes relationship for the teeth to mesh. For this purpose the tool column 18 has at the side thereof facing the work support a centering structure (not shown) and arcuate ways for the reception of clamping screws 28. The clamping screws extend through a tool head 30 which is thus angularly adjustable about a horizontal axis with reference to the tool column 13. The tool head 30 is provided with forwardly extending arms 32 which provide a pivot connection 34 for a swingable tool support or carrier 35. The tool support includes a spindle 36 in the form of a stub arbor supporting a tool 37. The tool support includes a platform 38 on which is mounted a motor 39 connected through a coupling 4t) to a pinion 41 which drives the spindle 36 through gears 42, 43, 44, 45 and 46.

From the foregoing it will be noted that the tool support 35 is mounted for rocking movement about the horizontal axis of pivot support 34. The pivot support 34 is substantially directly beneath the axis of the tool spindle 36 and hence, limited rocking movement of the tool support results in substantially horizontal movement of a tool toward and away from a work gear later to be described. In addition, it will be noted that the axis of the pivot support 34 is substantially beneath the center of mass of the tool support and hence, little effort is required to effect rocking movement of the tool support. More specifically, the axis of the tool support 54 is located to the right of the center of mass of the structure carried by the other structure as seen in FIGURE 2, and hence, a relatively small counterclockwise torque prevails, tending to move the tool 37 away from the work gear 47.

Mounted for supporting a work gear 47 is a work table 48 on which are mounted a headstock 5t and tailstock 52. The work table 48 is pivoted by means of a depending pivot pin 54 which is received within bearings 56 located in a cylindrical well 58 attached to the base 10. This arrangement is best illustrated in FIGURE 1. To support the Work table 48 for angular adjustment about the axis of the pivot pin 54 bearings 60 are provided interposed between hardened supports on the base and the adjacent surface of the work table 48.

It is desirable to provide means for effecting a relative rocking movement so that the gear finishing operation may if desired impart a crown shape to the teeth of the gear. It is for this reason that the work table 48 is mounted for rocking movement about a vertical axis. Cam means are provided for effecting a small angular rocking movement of the work table in timed relation to traverse of the tool slide 16. This means, best seen in FIGURES 4 and 5, comprises an angularly adjustable cam 62 on the tool slide 16 having a longitudinally extending groove 64 therein. Extending rearwardly from the work table 48 is a rigid arm 66 having a depending pin 68 adapted to be received in the groove 64. The cam 62 may be locked in angularly adjusted position by suitable means indicated at 70 in FIGURE 5. It will be appreciated that if the groove or slot 64 is parallel to the direction of reciprocation of the tool slide 16, traverse of the tool slide does not result in rocking of the work table 48. However, if the cam 62 is adjusted a desired back and forth rocking movement of the work table in timed relation to traverse of the tool slide is produced.

The mechanism for effecting traverse of the tool slide 16 comprises a pinion 72 driven by the motor 12 and driving a gear 74. The gear 74 in turn drives a pinion 76 of a pump 78. In addition, the gear 74 connects to a pinion 80 driving a gear 82 which in turn is connected to a pinion 84 driving a gear 86. The latter is connected to a pinion 88 which is in mesh with a gear 9i) keyed or otherwise secured to a feed screw 92 received in a feed nut 94. The feed screw 92 is journaled in the base and the nut is rigidly connected to the tool slide. Accordingly, operation of the motor 12 results in traverse of the tool slide 16.

Specifically, the rocking movement of the tool support 35 is accomplished by means of a lever 96 pivoted as indicated at 100 and connected by a link 102 to a pivot connection 104 carried by the tool support 35. The lever 96 is connected to a link 186 having a head 108 engaging a compression spring 118. The spring 110 thus exerts a force to the left on the link 1186 tending to rock the lever 96 counterclockwise and to swing the tool support 35 clockwise to cause the tool 37 to approach the work gear 47. The strength of the spring which of course may be adjusted by suitable adjustment of the head 108, thus causes the mechanism to swing the tool support 35 toward the work to establish a predetermined pressure between the teeth of the gear and tool.

Means are provided for overcoming the force of the spring to retract the tool and this means comprises a cylinder 112 receiving a piston 114 carrying a plunger 116 engageable with the upper end of the lever 96. When air is admitted to the cylinder 112 the lever is swung clockwise, thus retracting the tool from the work.

An adjustable abutment 118 is provided in the cylinder which limits feed of the tool to the work.

Referring now to FIGURE 6 there is illustrated mechanism which guides the movement of the tool support 35. For this purpose the tool support 35 carries a block 120 having a recess 122 therein which receives a hardened plug 124 projecting forwardly from the face of the tool head 30. Received in cylindrical openings 126 in the block 128 are balls 130 which may be pressed into engagement with the sides of the hardened plug 124 by screws 132 in cooperation with slidable ball engaging elements 136.

An adjustable abutment screw 138 is provided to limit relative movement between the tool head and pivotally mounted tool support in one direction.

Preferably, means are provided which are effective to prevent or oppose separation between the work gear and tool during the operation but which permits continued approach between these members as may be re- 4 quired upon removal of stock from the work gear. This means is best illustrated in FIGURE 2 where it will be observed that the link 106 includes an inclined cam surface 140 adapted to be engaged by a correspondingly inclined end of a piston rod 142 connected to a piston 144 in a cylinder 146. The operation of this mechanism permits the tool to move into engagement with the work gear 47 at a relatively light pressure as determined by the effectiveness of the spring 110. Air is thereupon applied to the cylinder 146 and the piston rod 142, engaging the cam surface 140 at an angle, which provides an additional force opposing separation between the work gear 47 and the tool 37. However, the tool 37 is permitted to move further to the right, as may be occasioned by stock removal or by reason of initial engagement between the gear and tool at a high point on the eccentric gear. I

It will be recalled that the mechanism for moving the tool away from the Work gear also includes the fluid pressure and cylinder device including the cylinder 112. The cylinders 112 and 146 are preferably connected so that when fluid pressure is applied thereto the locking cam structure 140, 142 is released to permit retracting movement of the tool 37 by the piston 114.

Referring now to FIGURES 7-9 there is illustrated a somewhat different embodiment of the present invention. The structure for supporting the honing tool herein designated 159 may be exactly the same as the mechanism for supporting the tool shown in FIGURE 2 and accordingly, the description will not be complicated by repeating a description of the details. In the present case however, rather than mounting the tool supporting and driving mechanism on the slide 16 shown in FIGURE 2, the tool supporting and driving mechanism herein designated 152 is mounted on a stationary portion of the base 154 and in this embodiment of the invention a slide 156 is provided which includes means for mounting a work gear 158 thereon for rotation. This means includes a head or tailstock designated 160.

The means for effecting horizontal traverse of the work support includes the ways 162 and a feed nut diagrammatically indicated at 164 depending from the slide 156. A feed screw 166 is in threaded engagement with the nut and rotation of the feed screw effects horizontal back and forth reciprocation of the slide 156 parallel to the ways 162. The means for effecting rotation of the feed screw 166 is substantially similar to that for effecting rotation of the feed screw 92 and comprises a pinion 168 driven by a motor 170 and in turn driving a gear 172. The gear 172 in turn drives a pinion 174 of a pump 176. In addition, the gear 127 is connected to a pinion 178 driving a gear 180 which in turn is connected to a pinion 184 driving a gear 186. The latter is connected to a pinion 188 which is in mesh with a gear 190 keyed or otherwise secured to the feed screw 166. The feed screw 166 is journaled in the base and the nut, as previously noted, is rigidly connected to the slide 156. Accordingly, operation of the motor 176 results in traverse of the slide 156.

In this embodiment of the invention the tool support head 192 is angularly adjustable about a horizontal axis to provide for the crossed axes relationship between the honing tool 150 and the work gear 158 as in the embodiment previously described. In addition, means are provided for effecting angular adjustment of the gear 158 about 'a horizontal axis extending perpendicularly to the axis of the honing tool and gear. This arrangement is best illustrated in FIGURE 8 where it will be observed that a table 193 includes a downwardly extending arcu ate portion 194 which is associated with a correspond ingly shaped guiding recess on a slide 196 corresponding generally to the slide 156 disclosed in FIGURE 7. Preferably, the downwardly extending arcuate portion 194 includes a segment 198 of worm gear teeth in mesh with an adjusting worm 200 which includes an operating shaft gear-like tool.

202 and a square end 2&4 for engagement by a suitable tool.

The slide 196 includes a depending feed nut 206 cooperating with a feed screw 2%, the feed screw being driven by gearing indicated generally at 210 which may be identical with the feed transmission mechanism illustrated in FIGURE 7.

The table 193 is adapted to be locked in angularly adjusted position by means of threaded bolts 212 cooperating with nuts 214 having spherical bearings 216 associated therewith. The table 193 includes a tailstock 218 and a headstock 220 for supporting the work piece indicated at 222 therebetween.

It will be apparent that the work piece 222 may be angularly adjusted about a horizontal axis indicated at 224 which is the center of curvature of the arcuate guide surfaces between the table 193 and the slide 196. The crossed axes setting between the work gear 222 and the gear like cutter carried by the tool head 192 can be made by effecting angular adjustment of the tool supporting head 192 about a horizontal axis extending through the The relative traverse between the gear and tool is always accomplished by relative horizontal traversebetween the gear and tool, and in the embodiment of the invention illustrated in FIGURES 79 this is accomplished specifically by moving the work piece horizontally.

It will be apparent from the foregoing that the present apparatus provides means for effecting the gear finishing operation known to the industry as diagonal traverse gear finishing, by adjusting 'the axis of the work gear out of horizontal to provide a desired angle between the direction of traverse and the axis of the work gear.

It will of course be apparent that the angular adjustment of the work gear as specifically illustrated in FIG- URES 8 and 9, may also be applicable to the embodiment of the invention illustrated in FIGURES 1-4.

The drawings and the foregoing specification constitute a description of the improved gear finishing machine in such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims.

What I claim as my invention is:

l. A gear finishing machine comprising a base, a first rotary support mounted on said base for supporting a first rotary member for rotation about its axis, a slide on said base mounted for reciprocation thereon in a direction parallel to the said axis of rotation, a column mounted on said slide for adjustment thereon toward and away from said first rotary support, an adjustable head mounted on said column for angular adjustment about an axis perpendicular to the direction of reciprocation of said slide and substantially intersecting the said axis of rotation, a second rotary support for a second rotary member pivoted to said adjustable head for rocking movement about an axis parallel to the direction of reciprocation of said slide, the axis of rotation of said second rotary member being substantially adjacent a vertical plane passing through the pivot axis between said head and second rotary support whereby rocking movement of said second rotary support causes the second rotary member carried by said second rotary support to move substantially directly toward and away from the first rotary member carried by said first rotary support, means for driving one of the rotary members directly, means for efiecting reciprocation of said slide, and progressively operable yieldable means elfective to rock said pivotally mounted rotary support about its pivot mounting to effect controlled pressure contact between said rotary members.

2. A gear finishing machine as defined in claim 1 in which the pivot connection between said second rotary support and said adjustable head is located substantially directly below and parallel to the axis of said second rotary member.

3. A gear finishing machine as defined in claim 1 comprising resilient means connected to said second rotary support to urge it toward said first rotary support, and fluid pressure actuating means for retracting said second rotary support against the action of said resilient means.

4. A gear finishing machine as defined in claim 3 comprising lock means for locking the second rotary support in a position determined by engagement between the rotary member at a pressure therebetween as determined by said resilient means.

5. A gear finishing machine as defined in claim 1 comprising guide means intermediate said second rotary support and said adjustable head positioned at a point remote from the axis of the pivot means intermediate said second rotary support and said adjustable head.

6. A gear finishing machine as defined in claim 5 in which said guide means comprises a guide element disposed between a pair of balls.

7. A gear finishing machine comprising a base, a first rotary support mounted on said base for supporting a first rotary member for rotation about its axis, means connecting sm'd first rotary support to said base for angular movement about an axis perpendicular to the axis of rotation, a slide on said base mounted for reciprocation thereon in a direction parallel to the said axis of rotation, a column mounted on said slide for adjustment thereon toward and away from said first rotary support, an adjustable head mounted on said column for angular adjustment about an axis perpendicular to the direction of reciprocation of said slide and substantially intersecting the said axis of rotation, a second rotary support for a second rotary member pivoted to said adjustable head for rocking movement about an axis parallel to the direction of reciprocation of said slide, the axis of rotation of said second rotary member being substantially adjacent a vertical plane passing through the pivot axis between said head and second rotary support whereby rocking movement of said second rotary support causes the second rotary member carried by said second rotary support to move substantially directly toward and away from the first rotary member carried by said first rotary support, means for driving one of the rotary members directly, means for eiiecting reciprocation of said slide, progressively operable yieldable means effective to rock said pivotally mounted rotary support about its pivot mounting to effect controlled pressure contact between said rotary members, and adjustable cam means: disposed between said slide and said first rotary support to efiect swinging movement of said first rotary support about the axis of its connection to said base upon movement of said slide.

8. A gear finishing machine as defined in claim 7 in which said cam means comprises an adjustable member having an elongated cam slot and a cam follower movable in said slot, said cam member being selectively adjustable to a position in which said slot extends parallel to the direction of reciprocation of said slide or at a slight angle thereto.

9. A gear finishing machine comprising a base, a work support mounted on said base, a work support arbor on said work support, a tool slide mounted on said base for reciprocation thereon in a direction substantially parallel to the axis of said work support arbor, a column on said slide mounted for adjustment toward and away from said work support, a tool head mounted for angular adjustment on said column about an axis substantially perpendicular to and intersecting the axis of said work support arbor, a tool support pivoted to said tool head for rocking movement about an axis substantially parallel to the axis of said work support arbor, a tool support arbor on said tool support having its axis occupying a plane substantially parallel to the axis of the Work support arbor and substantially perpendicular to the axis of ad justment of said tool head, said tool support arbor being located in the vertical plane passing through the pivot connection between said tool support and said tool head whereby the torque produced by the weight of said tool support is minimized, and adjustable means connected to said tool support effective to urge said tool support and a tool mounted on said tool support arbor toward said work support and a work gear mounted on said work support arbor.

10. A gear finishing machine as defined in claim 9 in which the adjustable means for urging said tool support toward said work support comprises a lever pivoted to said tool head, a link connecting said lever to said tool support, spring means connected to said lever to urge said lever in a direction to cause said tool support to approach said work support.

11. A gear finishing machine as defined in claim 10 which comprises fluid actuated means connected to said lever for overcoming the force of said spring means to retract said tool support from said work support.

12. A gear finishing machine comprising a base, a Work support connected to said base for angular adjustment about a vertical axis, a horizontal work support arbor on said work support, a tool slide mounted on said base for reciprocation in a horizontal plane, a column mounted on said tool slide for horizontal adjustment toward and away from said work support, a tool head mounted on said column for angular adjustment about a horizontal axis substantially perpendicular to and intersecting the axis of said work support arbor, a tool support pivoted to said tool head for angular movement about a horizontal axis, a tool support spindle on said tool support located substantially in the vertical plane passing through the pivot connection between said tool support and said tool head whereby rocking movement of said tool support eifects movement of said tool support spindle for driving the same in rotation, and adjustable means connected to said tool support for developing a relatively small torque tending to move said tool support toward said work support to control pressure between the teeth of a work gear and gear-like finishing tool.

13. A gear finishing machine as defined in claim 12 comprising power means connected to said tool support for swinging said tool support away from said work support.

14. A gear finishing machine as defined in claim 12 including locking means effective to lock said tool support against movement away from said work support during operation.

15. A gear finishing machine comprising a rotary work support for mounting a work gear, a rotary tool support for mounting a gear-like tool in mesh with the work gear, means mounting one of said supports for movement to ward and away from the other, biasing means operative during movement of said one support for establishing a substantially constant continuously acting force tending to move said one support toward said other support to provide a minimum predetermined force acting radially between the gear and tool mounted on said supports, automatically operating blocking means continuously effective during a gear finishing cycle during which said one support approaches said other support as a result of the forces developed by said biasing means to prevent any reverse movement of said one support away from said other support, means for driving one of said supports in rotation, the other support being mounted for substantially free rotation, and means for effecting relative reciprocation between said supports in a direction which occupies a plane substantially parallel to the axes of both of said supports.

16. A gear finishing machine as defined in claim 15 comprising fluid pressure means connected to said movable support for effecting movement thereof away from the other support, and fluid pressure actuated means for said blocking means operable to release said blocking means to provide for ready separation between said supports.

17. A gear finishing machine comprising a base, work support structure including a rotary work support mounted on said base for supporting a work gear for rotation about its axis, tool support structure including a column on said base at one side of said work support and mounted for horizontal movement toward and away from said work support, an adjustable tool head on said column mounted for angular adjustment about a horizontal axis intersecting'the axis of said rotary work support, a rotary tool support pivoted to said tool head for rocking movement about an axis substantially parallel to the axis of rotation of said tool support, the axis of rotation of said rotary tool support being spaced a substantial distance from the pivot axis between said head and said tool support whereby rocking movement of said tool support about its pivot axis causes substantially direct relative approach and separation between said rotary work and tool supports, a slide movable horizontally on said base in a direction parallel to the vertical plane through the axis of rotation of said work support, said slide being interposed between said base and one of said support structures, means for driving one of said rotary supports directly, means for reciprocating said slide, and progressively operable yieldable means effective to rock said pivotally mounted work support about its pivot axis to elfect controlled pressure contact between said rotary Work gear and tool supports.

18. A machine as defined in claim 17 in which said slide is interposed between said base and said slide providing for the aforesaid movement of said column toward and away from said Work support.

19. A machine as defined in claim 17 in which said slide is interposed between said base and said work support structure.

20. A gear finishing machine comprising a base, a rotary tool support having its axis of rotation in a vertical plane, means mounting said rotary tool support on said base for angular adjustment on said base about a horizontal axis intersecting and perpendicular to the axis of rotation of said tool support and for adjustment horizontally on said base in parallelism to the horizontal axis of angular adjustment thereof, a work slide mounted for reciprocation on said base horizontally in a direction perpendicular to the axis of angular adjustment of said tool support, a work table having a rotary work support thereon having an axis of rotation occupying a substantially vertical plane parallel to the plane containing the axis of rotation of said tool support, adjustable means interconnecting said work table and said work slide to provide for angular adjustment of said rotary work support about a horizontal axis parallel to the horizontal axis of angular adjustment of said rotary work support and which is substantially coincident therewith when said work slide is in mid-position, means for driving one of said rotary supports directly, and means for reciprocating said slide.

21. A gear finishing machine comprising a base memher, a slide member mounted on said base member for horizontal rectilinear reciprocation thereon, a rotary work support carried by one of said members and having its axis of rotation horizontal and parallel to the direction of reciprocation of said slide member, a rotary tool support carried by the other of said members having its axis located in a vertical plane spaced laterally from the axis of rotation of said work support, means for adjusting said rotary tool support angularly about a horizontal axis perpendicular to and intersecting the axes of both of said rotary supports, a pivoted carrier for said rotary tool support having a pivot axis located substantially vertically spaced from a gear-like tool carried by said rotary tool support and substantially adjacent a vertical plane containing the axis of rotation of said rotary tool support to produce limited substantially horizontal movement of a tool toward and away from said work support upon rocking of said carrier, yieldable means operatively connected to said carrier to urge said carrier toward said work support with a predetermined force to control operating pressure between a tool and work gear carried by said rotary supports, means connected to one of said rotary supports to drive it in rotation, and means connected between said base member and slide member to reciprocate said slide member on said base member.

10 22. A machine as defined in claim 21 in which said rotary tool support is mounted on said slide member. 23. A machine as defined in claim 21 in which said rotary work support is mounted on said slide member.

No references cited. 

1. A GEAR FINISHING MACHINE COMPRISING A BASE, A FIRST ROTARY SUPPORT MOUNTED ON SAID BASE FOR SUPPORTING A FIRST ROTARY MEMBER FOR ROTATION ABOUT ITS AXIS, A SLIDE ON SAID BASE MOUNTED FOR RECIPROCATION THEREON IN A DIRECTION PARALLEL TO THE SAID AXIS OF ROTATION, A COLUMN MOUNTED ON SAID SLIDE FOR ADJUSTMENT THEREON TOWARD AND AWAY FROM SAID FIRST ROTARY SUPPORT, AN ADJUSTABLE HEAD MOUNTED ON SAID COLUMN FOR ANGULAR ADJUSTMENT ABOUT AN AXIS PERPENDICULAR TO THE DIRECTION OF RECIPROCATION OF SAID SLIDE AND SUBSTANTIALLY INTERSECTING THE SAID AXIS OF ROTATION, A SECOND ROTARY SUPPORT FOR A SECOND ROTARY MEMBER PIVOTED TO SAID ADJUSTABLE HEAD FOR ROCKING MOVEMENT ABOUT AN AXIS PARALLEL TO THE DIRECTION OF RECIPROCATION OF SAID SLIDE, THE AXIS OF ROTATION OF SAID SECOND ROTARY MEMBER BEING SUBSTANTIALLY ADJACENT A VERTICAL PLANE PASSING THROUGH THE PIVOT AXIS BETWEEN SAID HEAD AND SECOND ROTARY SUPPORT WHEREBY ROCKING MOVEMENT OF SAID SECOND ROTARY SUPPORT CAUSES THE SECOND ROTARY MEMBER CARRIED BY SAID SECOND ROTARY SUPPORT TO MOVE SUBSTANTIALLY DIRECTLY TOWARD AND AWAY FROM THE FIRST ROTARY MEMBER CARRIED BY SAID FIRST ROTARY SUPPORT, MEANS FOR DRIVING ONE OF THE ROTARY MEMBERS DIRECTLY, MEANS FOR EFFECTING RECIPROCATION OF SAID SLIDE, AND PROGRESSIVELY OPERABLE YIELDABLE MEANS EFFECTIVE TO ROCK SAID PIVOTALLY MOUNTED ROTARY SUPPORT ABOUT ITS PIVOT MOUNTING TO EFFECT CONTROLLED PRESSURE CONTACT BETWEEN SAID ROTARY MEMBERS. 